Hundreds of Victorian bus drivers will walk off the job, demanding better pay.
More than 600 drivers are expected to stop work after the last service on Monday and won't get behind the wheel again until the first scheduled service on Wednesday, meaning 70 trips will be cancelled.
The workers, employed by CDC which has a government contract to operate the bus services, want a four per cent wage rise and one per cent superannunation increase.
Transport Workers Union national vice-president John Berger says workers rejected a 2.5 per cent pay increase offer during discussions over the new enterprise bargaining agreement.
After a two-hour meeting on Monday, Mr Berger said negotiations had reached "an impasse" and he hoped a "suitable offer" would prevent the need for the strike, which would coincide with school holidays.
"We have not taken strike action in the bus industry for 20 years," he said.
"Increases in roadworks, traffic, level crossing removals they have to deal with and they get assaulted, sworn at and are not treated fairly by some members of the public."
More than 70 bus routes in Melbourne's east and west and Ballarat and Geelong will be affected, according to Public Transport Victoria's website.
CDC Victoria chief executive Nicholas Yap respected drivers' rights to take lawful industrial action but was disappointed it would cause "such a disruption".
"Our drivers do a very important job and we feel this wage offer demonstrates our support for them," he said of the increase rejected by drivers.
"We sincerely apologise to all customers and the community for disruptions that these actions will cause."
PTV chief executive Jeroen Weimar called on the union and CDC to quickly come to an agreement as the strike had the potential "to cause real inconvenience" to many passengers.
BUS ROUTES AFFECTED BY DRIVER STRIKE
* Melbourne: 150, 151, 153, 160, 161, 166, 167, 170, 180, 181, 190, 192, 400, 406-412, 414, 415, 417-419, 421, 423-425, 439, 441, 443, 461, 494- 498, 601, 605, 606, 612, 623-626, 630, 900
* Geelong: 1, 10, 11, 12, 20, 22, 23, 24, 25, 43
* All bus routes in Ballarat